S&S Cycle Top End Guardian Kit — 2017–2025 M8

Everything you need to update the M8 top end in one kit. The M8 makes serious power, but the top end has weak spots — S&S's Guardian kit addresses all of them: roller rocker arms, 66%-stronger rocker shafts, the rocker stud kit, and a head bolt kit. If you're doing a 124/128/131 conversion, S&S calls this kit a must-have.

FITMENT

Fits 2017–2025 Harley-Davidson M8 models (S&S). In our catalog: 2017–2025 M8 Touring models.

Not sure it fits your bike? Email info@norcalbaggersupply.com — email is the fastest way to reach us — and we'll confirm before you order. You can also call 916-626-9030 (Mon–Fri, 9 AM–5 PM PT).

CALIFORNIA / CARB

California / CARB: S&S Cycle publishes CARB Executive Order D-355-65 for this kit — it is exempt from emissions tampering regulations under that EO and is legal for sale and use in California on the models the Executive Order covers, as well as in all other states.

SPECIFICATIONS

• Manufacturer: S&S Cycle — part number 900-1092
• Includes S&S roller rocker arms — relieve the stress high-lift cams put on the valvetrain at high RPM (S&S)
• Rocker arm shafts 66% stronger than stock (S&S)
• Rocker arm stud kit — extends cylinder head life by preventing damage to the rocker arm towers (S&S)
• Head bolt kit: 8640 heat-treated steel, 200,000 psi ultimate tensile strength, cold-rolled threads and formed washers — durable and reusable (S&S)
• CARB Executive Order D-355-65 (S&S Cycle) — see the California note below
• Made in the USA

INSTALLATION

This is a full top-end job: rocker boxes and heads come apart. Follow the S&S instruction sheets included in the box and your Harley-Davidson service manual for torque specs and sequences. No official S&S install video is published for this kit — installation is manual-only. Professional installation is recommended; email us for an install-partner referral.

QUESTIONS RIDERS ASK

What's in the kit?
Roller rocker arms, the stronger rocker arm shaft set, the rocker arm stud kit, and the head bolt kit — the complete S&S top-end hardware update in one box.

Do I need this with a big bore kit?
S&S designed the Guardian kit to support 124/128/131 conversions and big cams — the stock top-end hardware is the weak link at that level. If you're building past a bolt-in cam, this is the insurance.

Can you ship this to California?
Yes. S&S publishes CARB Executive Order D-355-65 for this kit, so it is legal for sale and use in California on the models the EO covers — see the California note on this page.